test: Make this test runnable in directories with @ in their names

Jenkins likes to use directories with names involving the '@'
character, which breaks the sed expression in this test. Switch to use
'|' on the assumption that it's less likely to show up in a path.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220401 91177308-0d34-0410-b5e6-96231b3b80d8